CN102798751A - Novel voltage stability detection method - Google Patents

Abstract

The invention discloses a novel voltage stability detection method. Through analysis on the various conventional voltage stability judgment methods based on a single-port impedance matching method, the conventional methods have obvious in errors in the aspect of margin estimation and are not suitable for a multi-load system. In order to overcome the shortcoming, on the basis of the single-port impedance matching method, an 'equivalent impedance matching' concept is supplied; all loads are transferred out of the equivalent system; and a power system is decomposed into a series of different single-port networks, namely 'coupled single-port' circuits. Under a coupling condition, interaction between the loads is simulated according to an impedance matching theory, so that an aim of monitoring the voltage stability on line is fulfilled. Theoretical analysis and simulation experiment verify the effectiveness of the method.

Description

A kind of novel voltage Detection of Stability method

Technical field

The present invention relates to a kind of novel voltage Detection of Stability method, relate in particular to a kind of electric system research field that belongs to.

Background technology

Voltage stability is one of problem of paying close attention to the most of power industry.The accident of having a power failure on a large scale several times in recent years is all relevant with collapse of voltage.The Prevention of Voltage collapse also needs a kind of effective on-Line Voltage stability monitoring instrument except the good off-line system planning practice of needs.In view of this consideration, a lot of scholars have proposed many on-Line Voltage stability indexs.

In these indexs, use local phasor measurement to judge that the technology of spread of voltage has caused experts and scholars' extensive concern.The main method of this type technology may be summarized to be: on bus, measure local voltage and current phasor, and then obtain the system Dai Weinan equivalent circuit that bus is from then on seen into.If the Dai Weinan equivalent impedance " coupling " of loaded impedance and system then is judged as spread of voltage.In other words, can estimate to be delivered to the peak power of local measurement point with the impedance matching state.This thinking principle simply and has proposed multiple embodiments.Document [B.Gao; G.K.Morison; And P.Kundur.Voltage stability evaluation using modal analysis [J] .IEEE Trans.Power Systems; Vol.7, pp.1529-1542, Nov.1992.] set forth a kind of local measurement that uses and calculated the digital relay of transmission system about the bus robustness.Document [K.Vu; M.M.Begovic, D.Novosel, et al.Use of local measurements to estimate voltage-stability margin.IEEE Trans.on Power Systems; Vol.14; No.3, pp.1029-1035, Aug.1999.] a kind of real-time adaptive discrimination method about threshold voltages such as Dai Weinan and impedance proposed.

Document [I.Smon; G.Verbic; And F.Gubina.Local voltage-stability index using Tellegen ' s theorem [J] .IEEE Trans.on Power Systems, vol.21, no.3; Pp.1267-1275, Aug.2006.] simplify the Dai Weinan Determination of Parameters with Teller with theorem.

The present invention is called " single port impedance match method " with the above-mentioned theoretical voltage stability decision method of impedance matching that comes from.Because this method only needs local information, so be easy to implement.But; [Y.Wang; W.Y.Li; And J.P.Lu.A new node voltage stability index based on local voltage phasors [J] .Electric Power Systems Research, pp.79 (2009) 265271.] there is obvious defects in this method: when estimating equivalent Dai Weinan parameter, need suppose that they all are constants.Yet this condition is difficult to satisfy in the collapse of voltage process, because system will experience lasting variation, reaches the idle restriction etc. of exerting oneself like line tripping, shnt capacitor switching, generator.This in addition method is not suitable for multiple load system.

Chinese patent 200810016922.6, document [Wang Yi, willow is scalded. based on the equivalent systematic parameter Tracking Estimation [J] of Dai Weinan. and electric power network technique, 2000; 24 (11): 28-30], [Liao Guodong, Wang Xiaoru. the voltage based on wide area measurement is stabilized in line monitoring method [J]. Proceedings of the CSEE, 2009; 29 (4): 8-13], [pay English, Li Xingyuan. the online in real time voltage stability based on Static Equivalent is analyzed [J]. Automation of Electric Systems, 1997; 21 (11): 25-28], [vast sea, Lu Jiping, Li Wenyuan; Deng. based on the Equivalent Model and the voltage stability index [J] thereof of localized network voltage phasor. Proceedings of the CSEE, 2008,28 (34): 52-58] though described voltage stability decision method only need detect voltage, current data at local bus; Easy to implement, but have obvious defects.At first, these class methods need suppose that these parameters all remain unchanged when estimating the Dai Weinan equivalent parameters, yet this condition is difficult to satisfy in the collapse of voltage process, and lasting variation all will take place total system (comprising the Dai Weinan equivalent parameters).Secondly, this type voltage stability decision method is not suitable for multiple load system yet, and the said voltage stability decision method of the application is applicable to multiple load system.

Summary of the invention

The object of the invention is exactly in order to address the above problem; A kind of novel voltage Detection of Stability method is provided; Through " single port impedance match method " analyzed and studied; The defective of proof the method, and then a kind of method for detecting voltage stability based on " equivalent impedance coupling " has been proposed on its basis.It has all loads is all moved on to and will through coupling condition, be simulated the interaction between load according to impedance matching principle by the outside of the system of equivalence, and then the advantage that voltage stability is predicted.

To achieve these goals, the present invention adopts following technical scheme:

A kind of novel voltage Detection of Stability method mainly comprises following step:

Step 1: the status condition of acquisition system real time execution: from the SCADA supervisory control and data aquisition system, obtain network admittance matrix Y; From the PMUs phasor measurement unit, obtain synchronous generator voltage phasor V _GLocal measurement is measured the voltage and current phasor of every bus; Estimation curve fitting parameter a, b and c;

Step 2: it is that each bar bus is set up the dummy load S about scale factor μ that linear function, polynomial function and the three kinds of models of exponential function that obtained by offline mode wherein a kind of comes _EqAdopt the single port impedance matching methods to calculate: the E of every bus _EqAnd Z _EqSaid E _EqAnd Z _EqBe respectively the threshold voltage such as grade and the equivalent impedance of the Dai Weinan of system equivalent circuit; Said three kinds of models are exactly three kinds of curves, and these three kinds of curves are used for the growth of match dummy load, with this as scale factor, i.e. the function of the growth of actual loading;

Step 3: calculate dummy load S _Eq

Step 4: the voltage stability margin that calculates each single port system; With corresponding equivalent electrical circuit E _Eq, Z _Eq, and S _Eq(μ) calculate the transmission limit of each coupled single-ended port system; Thereby realize the assessment of voltage stability.

Estimation curve fitting parameter a, b, c deterministic process do in the said step 1,

Step (1-1): the network matrix Y in the received data file, calculate Z matrix and Z _Self=Z _Ii(the female wire size of i=); A series of scale factors, the operation trend is calculated the line voltage distribution V and the line current I of every bus; Said Z matrix is a Y inverse of a matrix matrix;

Step (1-2): calculate virtual active power P with regard to each scale factor μ _cWith virtual reactive power Q _c

Step (1-3): estimate a with least square method, b, and c.

Three kinds of models in the said step 2 are respectively linear function, polynomial function and exponential function, respectively suc as formula shown in (10), (11) and (12):

X _c＝aX _L+b＝aμX ₀+b （10）

X _c＝(aμ ²+bμ+c)X _L＝(aμ ³+bμ ²+cμ)X ₀ （11）

X _c＝(aμ ^b+c)X _L＝(aμ ^b+c)μX ₀ （12）

X wherein _cBe virtual power, μ is a scale factor, X _LBe real power, X ₀Real power for actual motion point place; X is P or Q in the formula, and subscript L representes real power, and subscript c representes virtual power, the real power that subscript 0 is illustrated on the real time execution point; The number of times of polynomial function can change according to the performance of curve fitting; Said P or Q are respectively meritorious and reactive power.

Said step 3: calculate dummy load S _Eq:

S _eqn=S _cn+S _Ln

In the following formula, the span of n is a positive integer, S _Eqn: the bus load of n one port network; S _Cn: the dummy load of n one port network (power); S _Ln: the actual loading of n one port network (power).

The computing method of calculating the transmission limit of each single port system in the said step 4 are:

${(E_{\mathrm{eqj}}^2-2(R_{\mathrm{Lj}}{P}_{\mathrm{eqj}}+X_{\mathrm{Lj}}{Q}_{\mathrm{eqj}}))}^2=4({\mathrm{<figure-callout\; id="2"\; label="R\; Lj"\; filenames="HDA00002039188100022.png,HDA00002039188100041.png"\; state="\{\{state\}\}">R</figure-callout>}}_{\mathrm{Lj}}^{}+X_{\mathrm{Lj}}^2)({\mathrm{<figure-callout\; id="2"\; label="P\; eqj"\; filenames="HDA00002039188100022.png,HDA00002039188100041.png"\; state="\{\{state\}\}">P</figure-callout>}}_{\mathrm{eqj}}^{}+Q_{\mathrm{eqj}}^2)---\left(13\right)$

In the formula

P _eqj＝P _Lj+P _cj＝μ _maxP _0j+P _cj(μ _max) （14）

Q _eqj＝Q _Lj+Q _cj＝μ _maxQ _0j+Q _cj(μ _max) （15）

And μ _MaxThe transmission limit of representing each coupled single-ended port system, subscript 0 is represented operating point, and scale factor equals 1 under this operating point; Said P _CjAnd Q _CjBe respectively the meritorious and reactive power of the dummy load on the j bar bus, P _0jAnd Q _0jBe respectively the meritorious and reactive power of reality that actual motion is pointed out on the j bar bus, P _LjAnd Q _LjBe respectively the meritorious and reactive power of reality on the j bar bus, P _EqjAnd Q _EqjBe respectively the meritorious and reactive power of system's thevenin equivalent circuit of seeing on the j bar bus; Said subscript L representes real power, and subscript j representes j bar bus, and subscript c representes virtual power, and subscript eq representes thevenin equivalent circuit, R _LjAnd X _LjBe respectively the resistance and the reactance of the actual equivalent load impedance of j bar bus.

Beneficial effect of the present invention:

1 this ground voltage of needs, electric current phasor and generator port voltage phasor just can be estimated the load nargin of each bar bus.Therefore, can both obtain nargin result and might continue tracing system or bus nargin at any time.

2 have eliminated the demand to the Dai Weinan equivalent impedance.According to the reason of narrating in the foreword, power system impedance is difficult to accurately estimate and want the expensive time.The coupled single-ended mouth model that the present invention proposes has overcome an impedance match method major obstacles in practice.

3 have utilized the comprehensive network information (network matrix Y that from SCASDA, obtains and the generator port voltage that obtains from PMU) and have constituted a combined type measurement-calculating fundamental voltage Stability Monitoring System in the bus information (busbar voltage, electric current and power) of local measurement.

Description of drawings

Fig. 1 is the Dai Weinan equivalent circuit;

Fig. 2 is the P of all loads _MaxEstimated value and the comparison between the actual value;

Fig. 3 is that the equivalent Vs. multiport of single port is equivalent;

Fig. 4 is the multiport network system model;

Fig. 5 is that the coupled single-ended port system is equivalent;

Fig. 6 is by the approximate coupled single-ended port system of a dummy load;

Fig. 7 (a) is the comparison-meritorious number percent Pc-ratio (%) between coupled power and the load;

Fig. 7 (b) is the comparison-idle number percent Qc-ratio (%) between coupled power and the load;

Fig. 8 is the off-line learning flow process of estimation curve fitting parameter;

Fig. 9 (a) is the polynomial function coefficient to coupling active power (Pc);

Fig. 9 (b) is the polynomial function coefficient to coupling reactive power (Qc);

Figure 10 (a) is the estimation matched curve parameter-to coupling active power (P of coupled power _c) the polynomial function coefficient;

Figure 10 (b) be coupled power estimation matched curve parameter-to the coupling reactive power (Qc) the polynomial function coefficient;

Figure 11 is that the coupled single-ended mouth network of multiport electric system is equivalent;

Figure 12 is a whole implementation scheme process flow diagram of the present invention;

The maximum ratio factor of Figure 13 for estimating from different methods to get.

Embodiment

Below in conjunction with accompanying drawing and embodiment the present invention is described further.

The single port impedance match method

According to Circuit theory, under the impedance matching state, promptly | Z _Load|=| Z _System| the time, the power that is delivered to single port reaches maximum.This thinking can be used for design " distributed " cutting load scheme preventing collapse of voltage, and is as follows:

1) from system, keep apart a certain load bus (monitored bus) and regard the remainder of system as a Dai Weinan equivalent circuit, as shown in Figure 1.

2) use the impedance matching theory on by isolate bus and come predicted voltage stability margin (or load nargin).

3) nargin will trigger cutting load less than a certain threshold value.

Such scheme need be confirmed the Dai Weinan equivalent parameters Z of system _EqAnd E _EqChinese scholars have proposed the method for many these parameters of estimation.Nearly all method all is based on following theory:

$Z_{\mathrm{eq}}=\frac{V_k-V_k^{\&prime;}}{I_k^{\&prime;}-I_k}---\left(1\right)$

V in the formula _kAnd I _kBe load voltage phasor and the load current phasor that measures constantly at t, and V ' _kAnd I ' _kThen measure in the t ' moment.Equivalent voltage source can be determined by following formula:

E _eq＝Z _eqI _k+V _k (2)

Above-mentioned equation supposition is invariable at t and t ' moment Dai Weinan equivalent parameters.Just can reach the purpose that impedance is estimated through continuous repetition said process.According to the impedance matching condition | Z _Load|=| Z _Eq|, can access the peak power P that is delivered to measurement point _MaxPairing peak power is:

$S_{\max }=\frac{\left|{\mathrm{<figure-callout\; id="2"\; label="E\; eq"\; filenames="HDA00002039188100022.png,HDA00002039188100041.png"\; state="\{\{state\}\}">E</figure-callout>}}_{\mathrm{eq}}^{}\right|\left[\right|Z_{\mathrm{eq}}|-(\mathrm{imag}\left(Z_{\mathrm{eq}}\right)\sin \mathrm{\&delta;}+\mathrm{real}\left(Z_{\mathrm{eq}}\right)\cos \mathrm{\&delta;})]}{2{[\mathrm{imag}\left(Z_{\mathrm{eq}}\right)\cos \mathrm{\&delta;}-\mathrm{real}\left(Z_{\mathrm{eq}}\right)\sin \mathrm{\&delta;}]}^2}---\left(3\right)$

S in the formula _MaxFor being studied the maximum applied power of bus, δ representes Z _EqPower-factor angle.Corresponding voltage stability margin is:

Above-mentioned single port impedance match method (being designated as the Z matching method) is effective to the linear impedance basic circuit.Yet for electric system, load is non-linear (a permanent power type) and be dynamic (the load restoration characteristic is arranged).When the Z matching technique is applied to this system, be all to be reduced to equivalent system impedance with being studied other outer all loads of load.But this way is infeasible.The result who on the IEEE30 bus-bar system, calculates, as shown in Figure 2, P on some bus has been described _MaxEstimated value significantly greater than its actual value.This situation will cause the load excision not enough.

Above-mentioned analysis shows that there is the error of can not ignore in the Z matching method in nargin is estimated.These problems all are that the essential defect by the Z matching technique causes.Therefore, the single port impedance match method can not adapt to multiple load system.

2 equivalent impedance matching methods

The essential defect of impedance match method is that all non-linear and dynamic loads all comprise in the system equivalent with other.Even their power level is constant, also can not be shown as single Z to these loading liquifiers _EqValue.Just can overcome this defective if all loads all are placed on etc. the outside of valve system, as shown in Figure 3.The equivalent notion of multiport network that Here it is.

At the beginning of the seventies, many scholars did large-scale research and analysis to the multiport impedance matching.Its research mainly is conceived to obtain the optimal network structure problem of maximum power transfer.But because power transmission network has existed and can not have been changed easily in electric system, so the multiport impedance matching can not be applied in the electric system.Therefore the present invention proposes the method for equivalent impedance coupling.

The multiport network Equivalent Model is as shown in Figure 4.All generators and load bus are separated into power supply and load respectively.Power transmission network is converted into an equivalent impedance matrix Z _EqSo the multiport electric system can be described by following formula.

V _L＝KE-Z _eqI _L (5)

E=[E in the formula ₁E ₂... E _m] ^T, V _L=[V _L1V _L2... V _Ln] ^T, I _L=[I _L1I _L2... I _Ln] ^T, K is the n that from system's admittance matrix, an obtains * m matrix, Z _EqIt is the system impedance matrix of a n * n.For load bus j, above-mentioned equation provides following formula:

$V_{\mathrm{Lj}}={\left[\mathrm{KE}\right]}_j-Z_{\mathrm{LLjj}}{I}_{\mathrm{Lj}}-\underset{i=1,i\&NotEqual;j}{\overset{n}{\mathrm{\&Sigma;}}}{Z}_{\mathrm{LLji}}{I}_{\mathrm{Li}}=E_{\mathrm{eqj}}-Z_{\mathrm{eqj}}{I}_{\mathrm{Lj}}-E_{\mathrm{coupled}-j}---\left(6\right)$

Z in the formula _EqjBe the equivalent impedance that do not comprise load of network at bus j place.Z _EqjEqual the short-circuit impedance seen into by bus j place in fact.As long as system topological remains unchanged Z _EqjIt is exactly a constant.E _Couple-jRepresent the influence of other load, be referred to as coupling effect in the present invention the voltage on the bus j.

The equivalent circuit of formula (6) is as shown in Figure 5.This is an one port network, and can be applied to all load bus.Compare with traditional single port equivalent circuit, increased a unique known variables E who represents other load to the influence of bus equivalent circuit _Couple-jAccording to the method, an electric system can be decomposed into a series of approximate one port networks that have no.In the present invention, this new equivalent circuit is called as " coupled single-ended mouth circuit ".

Because coupled single-ended mouth circuit E _CoupleAs an independent parameter, rather than E _CoupleBe integrated into Dai Weinan equivalent circuit voltage source E _EqWith internal resistance Z _EqIn.Therefore the enough simpler modes of its ability are improved the performance of impedance matching Basic Law.

Based on above analysis, if can estimate coupling effect effectively, the voltage stability prediction accuracy will improve greatly so.Analyze for ease and calculate, the present invention is approximately an excess power demand on bus j with coupling condition, and is referred to as dummy load S to it _Cj, as shown in Figure 6.Dummy load is confirmed by formula (7).

$S_{\mathrm{cj}}=P_{\mathrm{cj}}+j{Q}_{\mathrm{cj}}=E_{\mathrm{couple}-j}{I}_{\mathrm{Lj}}^{*}---\left(7\right)$

The characteristic of dummy load is as shown in Figure 7.Curve is the number percent of dummy load about actual loading among the figure, is defined as:

P _c-ratioj＝P _cj/S _Lj×100% (8)

Q _c-ratioj＝Q _cj/S _Lj×100% (9)

Can know, but have some to bear although most meritorious dummy load is positive by Fig. 7 (a).For both of these case, meritorious dummy load is along with the growth of actual loading (scale factor μ) increases with a kind of nonlinear way.Although rate of growth is very high near collapse of voltage point the time, virtual active load has only been represented a very little part (less than 12%) with respect to actual loading.

Yet the growth of the virtual reactive load shown in Fig. 7 (b) is to a great extent faster than actual loading and can reach 70% of actual loading.This explanation reactive power has the influence of can not ignore for collapse of voltage.Therefore, the non-linear growth of simulation dummy load is necessary for the power margin of each bar bus of accurate estimation.

The present invention proposes the growth that three kinds of curve fitting methods are similar to dummy load, with this function as scale factor (being the growth of actual loading).They are linear function, polynomial function and exponential function, respectively suc as formula shown in (10), (11) and (12):

X _c＝aX _L+b＝aμX ₀+b (10)

X _c＝(aμ ²+bμ+c)X _L＝(aμ ³+bμ ²+cμ)X ₀ (11)

X _c＝(aμ ^b+c)X _L＝(aμ ^b+c)μX ₀ (12)

X is P or Q in the formula, and subscript L representes real power, and subscript c representes virtual power, and subscript 0 is illustrated in the real power on the real time execution point (being the point of estimated voltage stability margin).The number of times of polynomial function can change according to the performance of curve fitting.

The present invention adopts the mode of off-line research to come estimated parameter a, b and c.The process of estimating these parameters is as shown in Figure 8.After the value of these parameters is determined, just can process a form to them, carry out online nargin through tabling look-up and estimate.

Estimate that by above-mentioned steps the polynomial function coefficient that obtains is as shown in Figure 9.The physical significance of map parameter is: they have described the degree of coupling between each bar bus and other bus of system.Wherein, the size of a parameter is represented the degree of coupling of this bus and other bus of system.The bus that a more parameters is big like bus 29, shows that the degree of coupling of other bus of it and system is high more.In addition, electric main road or generator cause because the voltage stability problem of system is normally by losing, so the N-1 accident is not allowed to ignore for the influence of these coefficients yet.Shown in figure 10, the figure middle polyline has been represented the coefficient that on each bar load bus under the different accident situation, obtains respectively.The result is illustrated in most cases, and these coefficients all remain unchanged.This just means only needs to confirm that through lookup table limited several coefficients get final product.

The method approximate to virtual power that proposes according to the present invention, the electric system of a complicacy can be broken down into one group of one port network shown in figure 11.In this figure, the bus load is the combination of virtual and actual loading as shown in Figure 6.

Utilization coupled power model, the transmission limit of each coupled single-ended port system is designated as μ _Max, can both calculate and get by formula (13).Here it is, and the PV of single port system curve reaches the standard [1] of its nose point:

${(E_{\mathrm{eqj}}^2-2(R_{\mathrm{Lj}}{P}_{\mathrm{eqj}}+X_{\mathrm{Lj}}{Q}_{\mathrm{eqj}}))}^2=4({\mathrm{<figure-callout\; id="2"\; label="R\; Lj"\; filenames="HDA00002039188100022.png,HDA00002039188100041.png"\; state="\{\{state\}\}">R</figure-callout>}}_{\mathrm{Lj}}^{}+X_{\mathrm{Lj}}^2)({\mathrm{<figure-callout\; id="2"\; label="P\; eqj"\; filenames="HDA00002039188100022.png,HDA00002039188100041.png"\; state="\{\{state\}\}">P</figure-callout>}}_{\mathrm{eqj}}^{}+Q_{\mathrm{eqj}}^2)---\left(13\right)$

In the formula

P _eqj＝P _Lj+P _cj＝μ _maxP _0j+P _cj(μ _max) (14)

Q _eqj＝Q _Lj+Q _cj＝μ _maxQ _0j+Q _cj(μ _max) (15)

And subscript 0 is represented operating point, and scale factor equals 1 under this operating point.

Therefore, through said method can this coupled single-ended mouth of On-line Estimation electric power system model voltage stability limit and nargin, and can define the lower voltage stability level or the zone of fragile bus.The whole implementation scheme of the method is shown in figure 12.

Implementation step is:

● the status condition of acquisition system real time execution: the network admittance matrix Y that from SCADA (supervisory control and data aquisition system), obtains, the synchronous generator voltage phasor V that from PMUs (phasor measurement unit), obtains _G, the voltage and current phasor of local measurement.

● it is the dummy load S of each bar bus foundation about scale factor μ that the three kinds of models (shown in (10), (11) and (12)) that obtained by offline mode that propose with the present invention wherein a kind of comes _Eq

● with obtaining the model of coupled single-ended port system like the described dummy load of Figure 11 (the coupled single-ended mouth network equivalent circuit of multiport electric system).

● with formula (13), (14) and (15) is each single port system-computed voltage stability margin.

The validity of the coupled single-ended mouth method that the present invention proposes and dummy load thereof are approximate shown in figure 13.In this figure, linear function model μ _EstObtain by of the variation of hypothesis coupled load, suc as formula (10) along with the linear function model; Polynomial function model μ _EstWith exponential Function Model μ _EstObtain by of the variation of hypothesis coupled load, respectively suc as formula (11) and (12) along with polynomial function model and exponential Function Model.The result shows as long as simulate coupling effect rightly, just can accurately estimate the power system voltage stabilization property limit.

Though the above-mentioned accompanying drawing specific embodiments of the invention that combines is described; But be not restriction to protection domain of the present invention; One of ordinary skill in the art should be understood that; On the basis of technical scheme of the present invention, those skilled in the art need not pay various modifications that creative work can make or distortion still in protection scope of the present invention.

Claims (5)

1. a novel voltage Detection of Stability method is characterized in that, mainly comprises following step:

Step 1: the status condition of acquisition system real time execution: from the SCADA supervisory control and data aquisition system, obtain network admittance matrix Y; From the PMUs phasor measurement unit, obtain synchronous generator voltage phasor V _GLocal measurement is measured the voltage and current phasor of every bus; Estimation curve fitting parameter a, b and c;

Step 2: it is that each bar bus is set up the dummy load S about scale factor μ that linear function, polynomial function and the three kinds of models of exponential function that obtained by offline mode wherein a kind of comes _EqAdopt the single port impedance matching methods to calculate: the E of every bus _EqAnd Z _EqSaid E _EqAnd Z _EqBe respectively the threshold voltage such as grade and the equivalent impedance of the Dai Weinan of system equivalent circuit; Said three kinds of models are exactly three kinds of curves, and these three kinds of curves are used for the growth of match dummy load, with this as scale factor, i.e. the function of the growth of actual loading;

Step 3: calculate dummy load S _Eq

Step 4: the voltage stability margin that calculates each single port system; With corresponding equivalent electrical circuit E _Eq, Z _Eq, and S _Eq(μ) calculate the transmission limit of each coupled single-ended port system; Thereby realize the assessment of voltage stability.

2. a kind of novel voltage Detection of Stability method as claimed in claim 1 is characterized in that estimation curve fitting parameter a, b, c deterministic process do in the said step 1,

Step (1-1): the network matrix Y in the received data file, calculate Z matrix and Z _Self=Z _Ii, the female wire size of i=; A series of scale factors, the operation trend is calculated the line voltage distribution V and the line current I of every bus; Said Z matrix is a Y inverse of a matrix matrix;

Step (1-2): calculate virtual active power P with regard to each scale factor μ _cWith virtual reactive power Q _c

Step (1-3): estimate a with least square method, b, and c.

3. a kind of novel voltage Detection of Stability method as claimed in claim 1 is characterized in that three kinds of models in the said step 2 are respectively linear function, polynomial function and exponential function, respectively suc as formula shown in (10), (11) and (12):

X _c＝aX _L+b＝aμX ₀+b （10）

X _c＝(aμ ²+bμ+c)X _L＝(aμ ³+bμ ²+cμ)X ₀ （11）

X _c＝(aμ ^b+c)X _L＝(aμ ^b+c)μX ₀ （12）

X wherein _cBe virtual power, μ is a scale factor, X _LBe real power, X ₀Real power for actual motion point place; X is P or Q in the formula, and subscript L representes real power, and subscript c representes virtual power, the real power that subscript 0 is illustrated on the real time execution point; The number of times of polynomial function can change according to the performance of curve fitting; Said P or Q are respectively meritorious and reactive power.

4. a kind of novel voltage Detection of Stability method as claimed in claim 1 is characterized in that said step 3: calculate dummy load S _Eq:

S _eqn=S _cn+S _Ln

In the following formula, the span of n is a positive integer, S _Eqn: the bus load of n one port network; S _Cn: the dummy load of n one port network; S _Ln: the actual loading of n one port network.

5. a kind of novel voltage Detection of Stability method as claimed in claim 1 is characterized in that, fall into a trap the calculate computing method of transmission limit of each single port system of said step 4 are:

${(E_{\mathrm{eqj}}^2-2(R_{\mathrm{Lj}}{P}_{\mathrm{eqj}}+X_{\mathrm{Lj}}{Q}_{\mathrm{eqj}}))}^2=4(R_{\mathrm{Lj}}^2+X_{\mathrm{Lj}}^2)(P_{\mathrm{eqj}}^2+Q_{\mathrm{eqj}}^2)---\left(13\right)$

In the formula

P _eqj＝P _Lj+P _cj＝μ _maxP _0j+P _cj(μ _max) （14）

Q _eqj＝Q _Lj+Q _cj＝μ _maxQ _0j+Q _cj(μ _max) （15）

And μ _MaxThe transmission limit of representing each coupled single-ended port system, subscript 0 is represented operating point, and scale factor equals 1 under this operating point; Said P _CjAnd Q _CjBe respectively the meritorious and reactive power of the dummy load on the j bar bus, P _0jAnd Q _0jBe respectively the meritorious and reactive power of reality that actual motion is pointed out on the j bar bus, P _LjAnd Q _LjBe respectively the meritorious and reactive power of reality on the j bar bus, P _EqjAnd Q _EqjBe respectively the meritorious and reactive power of system's thevenin equivalent circuit of seeing on the j bar bus; Said subscript L representes real power, and subscript j representes j bar bus, and subscript c representes virtual power, and subscript eq representes thevenin equivalent circuit; R _LjAnd X _LjBe respectively the resistance and the reactance of the actual equivalent load impedance of j bar bus.

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